A 38-year-old woman from Delhi presents with a 2-month history of jaundice, pruritus, and fatigue. She denies fever, abdominal pain, or recent travel. On examination, she is afebrile, icterus is present, and there is no hepatomegaly or splenomegaly. Laboratory investigations show: total bilirubin 4.5 mg/dL (conjugated 3.2 mg/dL), ALT 68 U/L, AST 72 U/L, ALP 185 U/L, GGT 165 U/L. Serum antimitochondrial antibody (AMA-M2) is positive. Abdominal ultrasound is normal with no bile duct dilation. What is the most likely diagnosis?